Hi and welcome to the Flow forum. I am down the coast from you in San Diego, but I know Ojai and love the wines from that region. Like you, we have had a horrendous season this year, and have been feeding for much of the last 6 months.
Personally, I would harvest them (off the hives if the frames are not mostly capped, to prevent leaks into the brood nest) and then leave them off the hives until next year. I know you are in a botanic garden, but
- Are the flowers there producing nectar? Even in irrigated suburban San Diego, we have lots of flowers, but very little nectar. Our annual nectar flow is over by the beginning of July.
- Are the flowers producing nectar that honey bees can use? Many flowers are not suitable for honey bees, and are pollinated by other insects.
Don’t do that, please. You may encourage feral bees to come and rob your hives too! That would be terrible. You could harvest the honey as I suggested above and feed it back to your bees using an in-hive feeder (inverted mason jar, pail feed etc).
If there is honey in the frames, it may crystallize if refrigerated (it won’t in a freezer though). Also, if the frames are tilted and the honey is not capped, it will leak out. Believe me, I have done it. It even leaks from frozen frames, so store them upright.
My supers come off in July, and I start Oxalic Acid vapor treatments soon after that. If the mite counts are not down by September, I put Apivar strips into the hive. I am considering Randy Oliver’s oxalic acid sponge method, but this is not yet fully approved in California. Depends on whether you need to worry about such things. If you don’t have to worry about approvals, you could even leave your supers on with oxalic acid sponges… 
One other thing. If you leave your supers on, and there is not much of a nectar flow, expect huge amounts of propolis. That can jam up the opening mechanism big time, making the next harvest very difficult, or even impossible. That is why my supers come off. When the nectar flow stops, the propolis starts! 